2. Empyema

📄 Definition

Empyema = pus in the pleural space,

Almost always secondary to complicated pneumonia, chest surgery, trauma, or oesophageal rupture.

🛡️ Causes

🧠 Mnemonic: PECS

  • Pneumonia (bacterial – most common: Strep pneumoniae, Staph aureus, anaerobes)

  • Esophageal rupture (Boerhaave’s, iatrogenic)

  • Chest surgery / trauma

  • Seeding from bloodstream (sepsis, TB)

🔬 Pathophysiology

  • Parapneumonic effusion → infection → neutrophils + bacteria accumulate

  • Fibrin deposition → loculations

  • Formation of thick pus → restricts lung expansion

  • Can → sepsis, respiratory failure, chronic fibrothorax

 

🔍 Clinical Features

🧠 Mnemonic: PUS FLUID

  • Persistent fever despite antibiotics

  • Unilateral pleuritic chest pain

  • Shortness of breath

  • Foul-smelling sputum / purulent pleural fluid

  • Leukocytosis (↑WCC, ↑CRP)

  • Usually secondary to pneumonia

  • Irritability (esp. in children)

  • Dullness to percussion + ↓ breath sounds

🔬 Investigations 

StepInvestigationKey Findings / Exam Notes
1️⃣ First-lineCXRBlunted costophrenic angle, meniscus sign
 BloodsFBC ↑WCC, CRP ↑, blood cultures
2️⃣ ConfirmatoryUltrasound chest (US)Detects loculations, guides aspiration
 Diagnostic aspirationSend pleural fluid for pH, glucose, LDH, protein, Gram stain, culture
3️⃣ Advanced / problem-solvingCT chestDefines extent, identifies bronchopleural fistula, guides surgery

📊 Light’s Criteria – Exudate vs Transudate

🧠 Mnemonic: “Protein & LDH Light it up”

CriterionEmpyema Characteristic
Pleural:serum protein >0.5Yes → exudate
Pleural:serum LDH >0.6Yes → exudate
Pleural LDH >⅔ ULNYes → exudate

Pleural pH <7.2 strongly suggests empyema → needs drainage.

⚖️ Parapneumonic Effusion vs Empyema

FeatureSimple Parapneumonic EffusionEmpyema
FluidSterile, clearFrank pus / turbid
pH>7.3<7.2
GlucoseNormal<3.3 mmol/L
LDHMildly ↑Very high
ManagementMay resolve with abxRequires drainage + abx

💊 Management (Stepwise: BTS/NICE)

StepTreatmentNotes
1️⃣ First-lineIV antibioticsCo-amoxiclav, or ceftriaxone + metronidazole. Tailor to culture.
2️⃣ DefinitiveChest tube drainage (US/CT-guided)Required in almost all empyemas
3️⃣ If loculated / poor drainageIntrapleural fibrinolytics (tPA + DNase)Breaks down fibrin septations
4️⃣ Refractory / severeVATS or thoracotomy + decorticationIndicated if persistent sepsis, trapped lung
5️⃣ SupportNutrition, fluids, oxygen, analgesiaEspecially in children & frail adults

🧠 Mnemonic: PUS OUT

  • Pleural drainage (chest tube = definitive)

  • Ultrasound guidance (confirm & guide insertion)

  • Systemic antibiotics (start immediately, IV broad → culture-guided)

  • Optimise nutrition & supportive care

  • Use fibrinolytics (tPA/DNase if loculated)

  • Thoracics referral (VATS/decortication if refractory)

⚠️ Complications

  • Bronchopleural fistula

  • Fibrothorax (restrictive lung disease)

  • Sepsis / shock

  • Respiratory failure

  • Recurrent empyema

🔎 Key PARA Exam Traps

  • pH <7.2 = drain → don’t just “give antibiotics”

  • Ultrasound = first choice to confirm & guide aspiration (not CT)

  • Light’s criteria = exudate but pH is most specific for empyema

  • IV antibiotics + chest tube are both required → abx alone never enough

  • tPA/DNase = exam favourite for multiloculated cases

📅 Follow-up

  • Repeat imaging to confirm resolution

  • Continue antibiotics 2–6 weeks depending on response

  • Consider TB testing if high risk

  • Respiratory review ± surgical follow-up

Last updated in line with BTS Pleural Disease Guidelines & NICE Pneumonia NG138
Published: December 2018 • Last updated: August 2022
Last reviewed: July 2025
PASSMAP ensures all content is NICE-aligned and reviewed for Physician Associate Registration Assessment (PARA) success.

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